The present invention relates to vehicle exhaust systems and, more particularly, to a mounting connection for the suspension of engine exhaust pipes or the like.
Suspending an automotive exhaust system requires more than just rigidly mounting the system from the engine exhaust manifold to the body or frame of the vehicle. Designers must account for movement of the engine, the mass of the suspended system, the resultant system forces, and any noise or shock which might be transmitted to the vehicle passenger compartment. These are considerations which are not easily met with current solutions to the suspension of vehicle exhaust systems. Currently, one solution is to use a portion of an elastomer or webbing. To cope with these various requirements, currently, a rubber part, often called a "doughnut" because of its somewhat round torous like shape, is used between "hangers" that are attached to the vehicle and to the exhaust system, to support the exhaust system.
Considering the various noises, shocks, and forces that the suspension member must isolate from the vehicle body or frame, designer must take noise amplitude peaks into consideration. That is, the time between peaks of the noise frequencies, and the transmission of these various noises, shocks, and forces from the system to the vehicle body or frame must be considered. If one also considers the noises produced by the exhaust and engine, a very extensive frequency spectrum becomes apparent to the designer. A good suspension member must not transmit these frequencies to the vehicle attachment.
To overcome the frequency problem, elastomers, which do not transmit these frequencies would be a simple solution, however, elastomers will not resist considerable forces. If one considers that a portion of the exhaust system, like a catalytic converter, which may easily weigh 25 pounds and shock loads of 10 g "G's" could be imposed, yielding a sudden 8,000 lb. force, the magnitude of the problem of the elastomers becomes apparent. Other vehicle systems like the vehicle suspension system and tires, etc., act to limit the actual shock loads to lower values, but very high forces must be withstood in any case.
The method herein disclosed involves the use of a new type r of spring which is made from a flat strip of material, like stainless steel. This spring has a very high force per unit size and weight and its construction substantially prohibits noise frequency conduction. By encapsulating the spring in elastomeric material, which effectively absorbs the noise energy frequencies that would otherwise be transmitted, the spring provides a small and lightweight. The device converts the short time force frequencies into long time or ultra low frequency forces which limits, not only the peak amount of the noise amplitude, but the transmission of noise as well.
The suspension member includes a serpentine spring which has a first spring rate which carries the at rest mass and first accelerations of the suspended mass, and which has a different spring rate superimposed on the initial spring rate to resist attaching points by an elastomer, or by attaching the spring, in either case sustaining low level amplitudes of vibration associated with the conduction of noise by the means of a combined elastomer that is optimized for absorption of energy. The combination results in a low cost structure that is capable of suspending the exhaust system and prohibiting the transmission of shock and noise from the exhaust system to the fixed mounting area.
From the following detailed description taken in conjunction with the accompanying drawings and subjoined claims, other objects and advantages of the present invention will become apparent to those skilled in the art.